Let me give you my take on this, I personally believe the Sager 9750 has a compatibility issue with the X2 4400+ my friend. I have had this 9750 since it came out, running a 3500+ and it was FLAWLESS, I upgraded it recently to a X2 4400+ and I have the same issue. I have it plugged in, windows treats it like a desktop as it always did so i get full power. When playing games it will run great, the suddenly slow to a crawl for about 15-20 seconds.. as I watch my temps and CPU usage, the CPU usage drops out in those periods.. Today I downgraded my CPU and my problems went away. I want to try another X2 model and see if they work better.. but I know the 4400+ is the issue as I had the problem on both XP and VISTA.
from what I have gathered, this issue is specific to the 4400+
As for Sagers Support, they have been so awesome to me even though I purchased my system from PCTorque, they have answered my every email quickly, and have given me loads of help, I just think our issue is beyond thier abilities and they are not aware of it.